Furukawa S, Moore B C
Department of Experimental Psychology, University of Cambridge, England.
J Acoust Soc Am. 1997 Dec;102(6):3657-64. doi: 10.1121/1.420152.
This study examined how effectively information about amplitude modulation (AM) on two carriers is combined, and whether the detection of AM depends on the relative phase of the AM across carriers. Psychometric functions were measured for detecting 5-Hz sinusoidal AM of carriers with frequencies 1100 and 1925 Hz, with a mean level 65 dB SPL for each carrier. The carriers had a duration of 400 ms with 50-ms raised-cosine ramps on either side of this. A single cycle of 5-Hz sinusoidal AM (200 ms in duration) was imposed on the temporal center of the stimulus, with 100-ms steady-state fringes before and after the modulation. The modulators for the two carriers were either in phase or in antiphase. The modulation of each carrier was equally detectable, as determined in a preliminary experiment. A continuous pink noise background was used to mask the outputs of auditory filters tuned between the two carrier frequencies. There was no effect of relative modulator phase. However, performance was consistently better than predicted from the assumption that information about AM from the two carriers is processed independently and combined optimally. The results are discussed in terms of (1) predictions using Dau's "modulation filter bank model" [T. Dau et al., in Psychoacoustics, Speech and Hearing Aids, edited by B. Kollmeier (World Scientific, Singapore, 1996), pp. 45-48], and (2) the fact that relative modulator phase does have an effect on the detection of frequency modulation on two carriers, as found by Furukawa and Moore [J. Acoust. Soc. Am. 100, 2299-2311 (1996)].
本研究考察了关于两个载波上幅度调制（AM）的信息是如何有效组合的，以及AM的检测是否取决于跨载波的AM相对相位。测量了用于检测频率为1100和1925Hz载波的5Hz正弦AM的心理测量函数，每个载波的平均声压级为65dB SPL。载波持续时间为400ms，两侧有50ms的升余弦斜坡。一个持续200ms的5Hz正弦AM单周期被施加在刺激的时间中心，调制前后有100ms的稳态条纹。两个载波的调制器要么同相要么反相。如在初步实验中所确定的，每个载波的调制都同样可检测。使用连续的粉红噪声背景来掩蔽在两个载波频率之间调谐的听觉滤波器的输出。相对调制器相位没有影响。然而，性能始终优于基于两个载波的AM信息被独立处理并最优组合这一假设所做出的预测。根据（1）使用道的“调制滤波器组模型”[T. Dau等人，载于《心理声学、语音和助听器》，B. Kollmeier编辑（世界科学出版社，新加坡，1996年），第45 - 48页]所做的预测，以及（2）古川和穆尔[《美国声学学会杂志》100, 2299 - 2311（1996年）]所发现的相对调制器相位确实对两个载波上频率调制的检测有影响这一事实，对结果进行了讨论。
